1. Field of the Invention
The present invention is related to switching devices. More specifically, the present invention is related to switching devices comprising half-metals.
2. Related Art
Rapid miniaturization of semiconductor devices has dramatically reduced chip feature sizes. Today, manufacturing technologies can fabricate devices that are as small as hundred nanometers. Many experts believe that device dimensions are destined to enter the realm of quantum mechanics.
This development has offered an unprecedented opportunity to define a radically new class of devices that exploit quantum mechanics to provide unique advantages over existing device technologies.
One such quantum entity is known as spin, which is closely related to magnetism. Devices that rely on an electron's spin as well as their charge to perform computations have given rise to a new field called spintronics (short for spin-based electronics). Note that computing technology has thus far relied mostly on purely charge based devices that move electric charges around, without exploiting the information contained in the spin that tags along for the ride on each electron.
Spintronic devices made of metallic magnetic materials, which exploit the spin of electrons as well as their charge, have already yielded breakthroughs in data storage applications and semiconducting magnetic materials, and they hold the promise of doing the same for microprocessors and a host of other technologies. The success of these latter devices depends on the discovery of materials containing atoms having large atomic magnetic moments and high Curie temperatures.
Specifically, magnetically doped semiconductors are expected to be successfully used to create spintronic devices. These materials can exhibit very high atomic spin moments per magnetic atom. Unfortunately, because of the doping, incoherence of carrier transport can create serious problems in device performance. Furthermore, the most studied doped cubic semiconductor, Mn-doped GaAs, suffers from a low Curie temperature of 110 K. As a result, devices made of Mn-doped GaAs cannot be operated at room temperature.
Half-metals (HM) is a more promising class of materials that is being considered for spintronic applications. Half-metals are so named because one spin channel is metallic while the other is insulating or semiconducting. The polarization of the carriers in the occupied states at the highest energy, the Fermi energy (EF) is thus complete, contributed entirely by one spin channel at the intrinsic Fermi energy. This is in marked contrast to the usual ferromagnetic metals such as iron in which both spin channels contribute at the intrinsic Fermi energy, resulting in substantially less than 100% polarization.
Hence, what is needed is a new class of spintronic switching devices based on half-metals.